The present invention relates to a solar cell charger used in a portable device.
Recently, all types of electrical equipment have been miniaturized and converted to portable devices, e.g., notebook computer, personal digital assistant, mobile phone, and the like. These portable device require use of batteries for obvious reasons. A single-use batteries (e.g., dry-cell batteries) and rechargeable batteries (e.g., nickel-cadmium batteries) are well known battery power sources.
Today's portable electronic devices generally use rechargeable batteries for its convenience. Rechargeable batteries may be charged using alternating current (AC current) or solar energy. The alternating current requires a power socket that is connected to a power source. Accordingly, devices that use the AC currents to recharge generally cannot be used in outdoors. For this reason, it may be necessary to carry a spare battery if the portable device is to be used for extended time away from a power source.
Rechargeable solar energy batteries, however, can be charged generally anywhere, both indoors or outdoors, as long as there is light, thereby providing a greater flexibility to users. In addition, solar-cell batteries do not require any AC current conversion circuitry since only direct current is used, which simplifies circuitry and reduces manufacturing cost.
A typical solar cell based charger includes a solar cell, namely a photovoltaic device, batteries, associated electrical circuits, and the casing of the assembly. The solar cell 30 is generally mounted on the side of a container 10, as shown in FIG. 1. A core electronic component is provided within the container. When the core electronic component is inserted into the container via an opening 15, its batteries are charged with electrical energy by the battery module 20 of the container 10. The battery module 20 is charged by the solar cell 30. The battery module 20 contains power management electronic circuitry to operate as desired in these applications.
In a conventional technology, a solar cell is mounted on one of the external surfaces of the container, as shown in FIG. 1. In order for the solar cell to capture as much sun light as possible, it is desirable to cover as much of the surfaces of the container as possible with solar cells. The solar cell 30, having a lateral dimension of X, covers substantially all of the upper surface of the container 11 that has a lateral dimension Y. However solar cell material is more costly than the plastics, polymer, or metal that are generally used to make the container. In addition, solar cell material, especially, the semiconductor based solar cell, is brittle and may easily scratch or break in the daily handling of such a container.